Santorini Isn’t Alone

Just a couple months ago, I had no idea that the sea of Greece was home to a caldera much like the ones that I learned about in my introductory geology course the first semester of my time at Northern Arizona University. I have realized that many of the geological processes in the world have been left in the shadows and ignored. Traveling across the Atlantic ocean to Santorini, I have began to broaden my understanding of the forces of earth in this part of the world. As inspiration goes, I have been drawn further in my curiosity to wonder: Is Santorini, the floating volcano in the Aegean Sea, not alone?

Santorini and its volcanic history that has brought us overseas is very unique. Despite the educational potential of Santorini, our destination of study could have presented equal adventure elsewhere in the Aegean Sea. Santorini is only one of the volcanic giants that make up the South Aegean Active Volcanic Arc or ‘SAAVA’. A volcanic arc is created when a tectonic plate slides into the plastic like layer under the two layers of another tectonic plate. By doing so, the H2O from the subducting plate melts this layer ‘the asthenosphere’ into a liquid state at which it rises to the surface and creates volcanoes where the magma can get through.

The five main volcanic islands of the Aegean sea are Methana, Milos, Santorini, Nisyros and Kos which are all spaced out in a ‘U’ shape dipping down from the west and back up slightly to the east. The formation of islands create the SAAVA, a perfect travel path for a Greek island hopping vacation. The Aegean arc is much different from most arcs in a way that the volcanic islands decrease in age in a pattern from west to east. The ages of normal volcanoes of arcs, however, are all relative. The process for this anomaly is as rare as NAU students studying geology in Greece.  

Figure 1: Some basic geologic and geographic characteristics of the Aegean Sea including: The African plate sliding north beneath the Eurasian plate highlighted in red with yellow arrows showing direction, the volcanic zones that make up the South Aegean Active Volcanic Arc, the crustal extension in yellow above Crete, and the Anatolian fault in the north.

The first and oldest volcanic zone is located just south of Athens. The volcano is called Methana and the rock is around 4 million years old [2]. The island is composed of many small domes of cooled lava that once oozed out of the Earth [2]. No significant explosive eruptions have occurred throughout the creation of this island. The volcanoes are still active however the magma last reached the surface in the 1700 [2].

Milos is the second volcano and it is a composite cone. This volcano has been inactive for thousands of years and is estimated by carbon dating to be 3.5 Million years old [1]. 350 thousand years ago the volcano was highly explosive [1].

Santorini is third youngest of the arc at an age of 1.55 Million years old [1]. Tonight I will sleep on this not erupting, but active, caldera. The island has many major eruptions and the Minoan eruption in 1600 BC was the most significant because of its ash cloud that reached far into Turkey and Africa. Flows of lava have been forming a complex of cinder cones to make up the the Kameni shield volcanoes which sits in the sea surrounded by the ring shape of islands. The lava flows of the Kameni islands slowed to a stop in 1950 [1].

Between Nisyros and Kos lie numerous different types of volcanoes about 150 thousand years old [1]. A stratovolcano makes up the island of Nisyros and is still active. The last eruption was in 1888 with steam shooting out of the vent. Once in 1996, the island experienced severe seismic activity catching the wary attention of volcanologists. The stratovolcano of Nisyros sits on the rim of a caldera that is submerged in the sea from Nisyros to Kos. This volcanic zone is the youngest of the South Aegean Active Volcanic Arc.

Now the SAAVA is much different than the Aleutian Volcanic Arc of Alaska because of two main characteristics. The first process has been called subduction roll back. This occurred when the African tectonic plate dove diagonally down under the Eurasian plate, however the plate dropped and sunk more than it dove into the mantle which pulled the Eurasian crust back as it fell downward into the heat of the earth. With this pulling apart, the plates faulted giving the magma an easy passage upwards to form the first volcanoes of Methana and Milos. The second factor that has led to the unique SAAVA was the North Anatolian fault that broke and twisted much of the crust in the Aegean sea causing smaller faults to appear in a southwest to north eastward trend. These faults created more passages for the magma that has now created the volcanoes of Santorini, Nisyros and Kos. This can be seen in Figure 1. The subduction roll back and the North Anatolian fault are two oddities that have been added to what could have been a normal volcanic arc like the Aleutian of Alaska or Northern Cascade arc in the north west United States

I now understand much more of the Aegean Sea and the volcanoes of Methana, Milos, Santorini, Nisyros and Kos. The volcanoes have been specifically placed due to the African plate roll back and the North Anatolian fault. My mind has faulted with new concepts of the earths potential and leads me to wonder if even the South Aegean Active Volcanic Arc, in the same sense as Santorini, is not alone.


[1] Kokkalas, S, Aydin, A, 2013, tectonics, Geol. Mag, 150, N2, p 193-224.

[2] Wikipedia, 2015, Methana Volcano; (June 2015)

10 thoughts on “Santorini Isn’t Alone

  1. Ray – Great summary of volcanism in the Aegean. I really like your Figure as it shows a little bit of personality and creativity.

    Please check throughout for South Aegean Volcanic Arc and replace with ‘South Aegean Active Volcanic Arc” and “SAAVA”. P7 and P8 have some spelling errors ‘Agean, SAVA, and Aleutina’ – please correct.

  2. I started reading this too make fun of you while we were making pasta and I ended up finding it to be quiet fascinating. I had no idea there were two calderas in the Aegean. I want to know if eventually the Aegean could become one whole caldera since it turns every year or if that’s not a thing. I also like the map you drew because you got so in detail! Good job Ray!!

  3. Hi Ray,

    What I’m enjoying most about this post is that you bring enough of your perspective and opinion into the text to make it as much about as as the subject you’re studying. The tone and language of this blog is meant to be mostly casually while still showing that you are an informed writer, and I think you are doing that well for the most part. Your descriptions of the five main volcanic islands are short enough that I didn’t lose interest or get lost in unfamiliar information. If you do have any thoughts on the other islands, even just a little blurb, those paragraphs could benefit somewhat from some more of your personal voice.

    I like the map you made showing the volcanic activity in the area, and I think this post and future posts could benefit from more pictures (preferably taken by you). Pictures that you take work in a similar way as providing quotes or paraphrasing an outside source: it’s a different voice or type of evidence that adds some depth to your text. If you take the pictures yourself, it would also add a personal touch which is not a bad thing in a blog that is as much about you as it is about the volcanoes.

    A good thing to keep in mind is your audience, which is composed of people who are not entirely as well versed in geology and also not as lucky to be where you are. So, describing what you see and providing pictures that fit those descriptions is a fantastic way of bringing the reader to you and showing them what you want them to see.

    Justin Kanzler

    1. Justin,

      Reading over your summary of your thoughts on my work did help me to give an overall rating of my post. I do struggle with putting personal voice into a writing on a more scientific paper. However, reading my post over again, I can see how much of my audience might have trouble following the language of geology. Meaning dumbing it down could make room for personal tone. Thanks for writing Justin!


  4. Hi Ray.

    Overall, your post is well written and incredibly factual. At first I was worried that I would become lost in the science jargon, but your writing successfully introduced such terms and explained them in a way that made sense and flowed well. Your introduction clearly introduces the main questions that your entry will seek to explore. From the final sentence of your introduction paragraph it is clear that your post will speak on the existence of other volcanoes found in the Aegean Sea. Your second paragraph transitions smoothly to providing background information defining Santorini and categorizing it both geographically and as a part of SAAVA, which also reiterates and answers your original ideas of the various volcanoes of the Aegean Sea. Your post is factual and there is a clear sense of style and voice that provides much information while transitioning smoothly between content.

    Your middle portions did well with describing the various volcanoes of SAAVA but there was a lot of information that I was unable to distinguish from your ideas and those of your sources. Although you do provide citations, some use of quotes or paraphrasing would better separate your voice and writing from that of your sources. It may also move your writing away from what could be considered plagiarism and towards a more polished synthesis of sources.
    Great post, I learned quite a bit concerning the various volcanoes that make up SAAVA. It was a pleasure to read,

    Jose Martinez

    1. Jose,

      I appreciate you sharing your thoughts on my blog attempt to mix complex geology with my own personal voice and perspective. I find it kind of challenging to use my own tone, summarize a concept scientifically and explained it to an audience with “no” knowledge of my post. I can understand, however, that I may be able to do this by really dumbing it down, making room for personal interpretation. I will take your advice on citations in paragraph, separating them from tone and keeping them in source. Thanks again.


  5. This is possibly one of my favorite posts because it brought to my attention that not all calderas are mentioned to the public. It made me realize how uninformed I am about the geological settings of the globe. You learn in geology112 the basic geological settings of the globe and form that class I thought I knew everything but then you opened my eyes to all the possibilities around the world, for volcanoes. It makes me question, how many calderas can be found on earth, what the biggest one is, and why we really only focus on Yellowstone in the US when are dozens of other calderas around the world. This also helped me understand the geological settings of the Aegean better for the test we took earlier this week.

  6. Thanks for this eye-opening contribution. I was wondering if the recent series of seismic activity, that resulted in many more or less strong earthquakes in the Marmara and Aegean region, could be more than just continental drift evoked tectonic activity. The series of minor earthquakes that has been shaking up Bodrum (Turkey) and nearby Kos for about 2 months, made me wonder, if a possible submarine volcano could be reason for this terranian unrest. One question remains: Does the Akyarlar volcano in the vicinity of Bodrum, which has been dormant for quite a long time, belong to the SAAVA system?

    1. The seismic activity in the Kos area is related to tectonics, not undersea volcanism. There are complex sets of strike-slip and normal faults related to the tectonic escape of Anatolia and northward subduction of the African Plate under the Aegean microplate. I am not familiar with the activity of the Akyarlar volcano – unfortunately!

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